The development of plastic blood collection bags has facilitated the separation of donated whole blood into its various components and analogous products, including factors, concentrates, and therapeutic serum, thereby making these different blood products available as a transfusion product. The separation of a single unit of donated whole blood, about 450 milliliters in USA practice, into its components is typically accomplished by use of differential sedimentation using centrifugation, as is well known to those skilled in the art.
A typical procedure used in the United States, the citrate-phosphate-dextrose-adenine (CPDA-1) system, utilizes a series of steps to separate donated blood into three components, each component having substantial therapeutic and monetary value. The procedure typically utilizes a blood collection bag which is integrally attached via flexible tubing to at least one, and preferably two or more, satellite bags. Using centrifugation, whole blood may be separated by differential sedimentation into such valuable blood components as plasma, packed red cells (PRC), platelet-rich plasma (PRP), platelet Concentrate (PC), and cryoprecipitate (which may require extra processing in order to obtain). The plasma may itself be transfused into a patient, or it may be separated by complex processes into a variety of other valuable blood products.
With the passage of time and the accumulation of research and clinical data, transfusion practices have changed greatly. One aspect of current practice is that whole blood is rarely administered; rather, patients needing red blood cells are given packed red cells, patients needing platelets are given platelet concentrate, and patients needing plasma are given plasma.
For this reason, the separation of blood into components has substantial therapeutic and monetary value. This is nowhere more evident than in treating the increased damage to a patient's immune system caused by the higher doses and stronger drugs now used during chemotherapy for cancer patients. These more aggressive chemotherapy protocols are directly implicated in the reduction of the platelet content of the blood to abnormally low levels; associated internal and external bleeding additionally requires more frequent transfusions of PC, and this has caused platelets to be in short supply and has put pressure on blood banks to increase platelet yield per unit of blood.
One of the problems attendant with the separation of various blood components using a multiple bag system and centrifugation is that highly valuable blood components become trapped in the conduits connecting the various bags and in the various biomedical devices that may be used in the system. It is an object of this invention to provide apparatuses and methods which permit the recovery of these valuable blood components.
In blood processing systems, air, in particular oxygen, present in stored blood and blood components, or in the storage container, may lead to an impairment of the quality of the blood components and may decrease their storage life. More particularly, oxygen may be associated with an increased metabolic rate (during glycolysis), which may lead to decreased storage life, and decreased viability and function of whole blood cells. For example, during storage red blood cells metabolize glucose, producing lactic and pyruvic acids. These acids decrease the pH of the medium, which in turn decreases metabolic functions. Furthermore, the presence of air/gas in the satellite bag may present a risk factor to a patient's being transfused with a blood component. For example, as little as 5 ml may cause severe injury or death. Despite the deleterious effect of oxygen on storage life and the quality of blood and blood components, the prior art has not addressed the removal of gases from blood processing systems during the initial collection and processing steps. It is, therefore, an object of this invention to provide a sterile blood processing system in which gases present in the system are separated from the blood or blood product.
Another problem has been maintaining the sterility of the processing system. The word sterility, as used herein, refers to maintaining a system free from viable contaminating microorganisms. Exemplary methods of determining sterility include tests using fluid thioglycollate medium or using soybean-casein digest medium, described in more detail in the U.S. Code of Federal Regulations (21 CFR 610.12).